The present invention refers to the ciphering and deciphering of multimedia data and in particular to the ciphering and deciphering formats which can be used e.g. in the commercial marketing of multimedia data.
With the appearance of telecommunication networks and in particular because of the widespread use of personal computers capable of handling digital multimedia data, a need arose for the commercial marketing of multimedia data, such as e.g. digital audio data or digital video data. The telecommunication networks may e.g. be analog telephone lines, digital telephone lines, such as ISDN e.g., or also the Internet. On the part of commercial providers of multimedia products there is the need to sell or hire out multimedia data in such a way that a customer should be able to choose a certain product individually from a certain catalogue at any time, only the customer who pays for it being able to use the product of course.
In contrast to the known ciphered television programmes, such as e.g. the television channels Premiere or MTV, where the broadcast data are ciphered identically for all users, who have acquired a suitable deciphering device for an appropriate fee, the present invention provides methods and devices which make possible an individual, customer-selective ciphering and deciphering of multimedia data. In contrast to the cited television channels, which offer a fixed programme which the user must accept or reject in its entirety, the methods and devices of the present invention offer the customer a maximum freedom of choice, i.e. he must only pay for those products which he has actually used.
U.S. Pat. No. 5,369,702 discloses a system for increasing the security of a computer system in which individual users can utilize the system flexibly and efficiently. The method disclosed in this publication comprises the steps of accessing an object-oriented key administrator, selecting an object to be ciphered, selecting a label for the object, selecting an ciphering algorithm, ciphering the object according to the ciphering algorithm, labelling the ciphered object, reading the object label, determining an access authorization on the basis of the object label and deciphering the object if the access authorization is granted. A file xe2x80x9clabelxe2x80x9d consists of a series of letters or numbers, which may be ciphered or not ciphered. This file label is separate from a message but is assigned to the transmission of the message, the label also identifying the person, position, equipment and/or organization entitled to receive the assigned message, i.e. the multimedia data.
U.S. Pat. No. 5,319,705 relates to a method and a system for the secure distribution of a plurality of software files from a software distribution processor to a user processor, while the user processor is selectively enabled to use only a subset of a smaller plurality of software files. This is achieved by using a customer key having an unciphered customer key and a derived section which is derived from the customer number.
It is the object of the present invention to provide methods and devices for ciphering and deciphering multimedia data which, on the one hand, guarantee an effective copyright protection, and which, on the other, are capable of ciphering and deciphering individually requested data flexibly.
According to a first aspect of the present inventions method for ciphering multimedia data to obtain an ciphered multimedia file having a definition data block and a multimedia data block, comprising the steps of entering a definition data ciphering index in the definition data block which points to a definition data ciphering algorithm to be used for ciphering a section of the definition data block; entering a multimedia data ciphering index in the definition data block which points to a multimedia data ciphering algorithm to be used for ciphering at least part of the multimedia data block; entering a free index in the definition data block, the free index identifying a particular deciphering device with which the ciphered multimedia data can be deciphered beyond a specified period of time; selecting the definition data ciphering algorithm from a plurality of ciphering algorithms on the basis of the definition data ciphering index; selecting the multimedia data ciphering algorithm from a plurality of ciphering algorithms on the basis of the multimedia data ciphering index; ciphering the section of the definition data block with the definition data ciphering algorithm, the section of the definition data block not including the definition data ciphering index; and at least partially ciphering the multimedia data block with the multimedia data ciphering algorithm.
According to a second aspect of the present invention a method for deciphering multimedia data contained in a multimedia file having a definition data block and a multimedia data block, the definition data block including a definition data ciphering index, a multimedia data ciphering index, and a free index, comprises the steps of reading the definition data block; selecting a definition data deciphering algorithm from a plurality of deciphering algorithms on the basis of the definition data ciphering index; selecting a multimedia data deciphering algorithm from a plurality of deciphering algorithms on the basis of the multimedia data ciphering index; deciphering the ciphered section of the definition data block using the definition data deciphering algorithm; and deciphering the multimedia data block using the selected multimedia data deciphering algorithm, wherein the step of deciphering the multimedia data block is only continued beyond a specified period of time if the device for deciphering has a setting which is appropriate for the free index.
According to a third aspect of the present invention a device for ciphering multimedia data to obtain a ciphered multimedia file having a definition data block and a multimedia data block, comprises means for entering a definition data ciphering index in the definition data block, the definition data ciphering index pointing to a definition data ciphering algorithm to be used for ciphering a section of the definition data block; means for entering a multimedia data ciphering index in the definition data block, the multimedia data ciphering index pointing to a multimedia data ciphering algorithm to be used for ciphering at least part of the multimedia data block; means for entering a free index in the definition data block, the free index identifying the device for deciphering with which the ciphered multimedia data can be deciphered beyond a specified period of time; means for selecting the definition data ciphering algorithm from a plurality of ciphering algorithms on the basis of the definition data ciphering index; means for selecting the multimedia data ciphering algorithm from a plurality of ciphering algorithms on the basis of the multimedia data ciphering index; means for ciphering the section of the definition data block with the definition data ciphering algorithm, the section of the definition data block not including the definition data ciphering index; and means for at least partially ciphering the multimedia data block with the multimedia data ciphering algorithm.
According to a fourth aspect of the present invention a device for deciphering multimedia data contained in a multimedia file having a definition data block and a multimedia data block, the definition data block including a definition data ciphering index, a multimedia data ciphering index, and a free index, comprises: means for reading the definition data block; means for selecting a definition data deciphering algorithm from a plurality of deciphering algorithms on the basis of the definition data ciphering index; means for selecting a multimedia data deciphering algorithm from a plurality of deciphering algorithms on the basis of the multimedia data ciphering index; means for deciphering the ciphered section of the definition data block using the definition data deciphering algorithm; and means for deciphering the multimedia data block using the selected multimedia data deciphering algorithm, wherein the device for deciphering the multimedia data only continues to decipher the multimedia data block beyond a specified period of time if the device has a setting which is appropriate for the free index.
The present invention is based on the finding that an adequate copyright protection for audio and video products in the form of digital multimedia data can be guaranteed only if a secure ciphering is performed as immediately as possible after the production of the digital multimedia data, which e.g. are coded or compressed according to the known Standard MPEG Audio Layer 3. For persons skilled in the art it is obvious that the present invention is not confined to the use of data in the MPEG Layer 3 format but that also uncompressed multimedia data or multimedia data which have been compressed according to some other method can be used as well.
After the multimedia data have been ciphered by an ciphering device prior to storing/filing them, they can be requested individually by a user who is in possession of a suitable deciphering device. Only for the accomplishment of its objectives, however, may this deciphering device annul the ciphering protection surrounding the data, it being of great importance also that not every deciphering device is capable of reading the multimedia data but only the deciphering device of the customer who has paid for the multimedia data. It is also important that it should be made as difficult as possible if not impossible for the user to make unauthorized changes in the multimedia data themselves or in the ciphering.
If a user should attempt to change the multimedia data, it is preferable that the data should be completely unreadable. The fact that the ciphering device already generates ciphered files at its output, spreads the protection over the multimedia data practically at once, therefore guarantees that no unprotected data appear at the start of a transmission/storage chain.
The deciphering device is able to read the specially ciphered data. The method for ciphering multimedia data according to the present invention generates, in addition to the existing unciphered multimedia data, a definition data block which contains various items of information concerning the ciphering of the unciphered multimedia data and concerning general and special functions which can be performed by the present invention.
Some of the functionalities required of a deciphering device according to the present invention will now be described:
A deciphering device of the present invention should be able to implement a demo playback unit for audio data, which may be e.g. in the ISO/MPEG Layer 3 format, which only permits the first 20 seconds or so of an audio recording to be played back. In special circumstances it should also be possible for the demo playback unit to play back certain pieces of music for longer than 20 seconds for a particular customer. This is achieved by a so-called clearing or releasing of the bit stream, which is effected by means of certain entries in the definition data block.
Furthermore, the present invention should be able to implement a deciphering device, i.e. a playback unit, for audio data in the MPEG Layer 3 format, which allows only certain customers to play back a certain audio file. This contributes to the copyright protection for audio or video works, for which a playback should only be possible after payment of a fee.
In addition the present invention should implement a player which can not only play back the contents of an audio data file but which can also display certain supplementary information. This supplementary information (i.e. meta data) can be information on the artist, the playback time, and further information on the audio recording or e.g. also a picture of the record/CD sleeve.
An ciphering device according to the present invention is able to cipher multimedia data efficiently and securely. In addition the present invention implements a special functionality called the challenge-response method, which will be described in detail later.
This method permits the creation of pre-ciphered audio data, which are stored in a database which can be accessed very quickly by a customer, who uses a private key which is derived from the key actually used for ciphering the data, the customer being able, using his private key and his user index, to calculate for himself the key actually used for ciphering the data, whereupon the multimedia data which have been retrieved can be deciphered, e.g. to play them back.
As a result it is possible that for a large number of customers who retrieve the same piece, the piece need not be fully ciphered each time for each individual customer but that the data can be ciphered identically for all customers, each customer being able, however, to calculate for himself the key actually used by employing his private key and a response key disclosed by the ciphering device.
In the challenge-response method the individual ciphering for each individual user is therefore achieved not by means of a completely new ciphering of the multimedia data but simply by means of a comparatively small change in the definition data block, which in accordance with the present invention is appended to the multimedia data.
The ciphering according to the present invention thus creates a file format for the protection of multimedia data which is used in the deciphering according to the present invention in order e.g. to implement the functionalities described above.